Problem: $623 \times 5.1 = $
Explanation: ${6}$ ${2}$ ${3}$ ${5}$ ${1}$ ${\times\vphantom{0}}$ ${.}$ ${3}\times {0.1}= {0.3}$ ${3}$ ${20}\times {0.1}= {2}$ ${2}$ ${600}\times {0.1}= {60}$ ${6}$ ${3}\times {5}= {15}$ ${5}$ ${0}$ ${20}\times {5}+C{10}= {110}$ ${1}$ ${600}\times {5}+C{100}= {3100}$ ${1}$ ${3}$ ${+\vphantom{0}}$ ${3}$ ${1}$ ${7}$ ${7}$ ${3}$ ${+\vphantom{0}}$ ${3}$ ${1}$ ${7}$ ${7}$ ${3}$ ${.}$ The top number has $0$ digits to the right of the decimal. The bottom number has $1$ digit to the right of the decimal. The product has $0+1=1$ digit to the right of the decimal. $623 \times 5.1 = 3177.3 $